Hi!

It sounds like jms2win is capable of sharing users and virtuemart users, but can I share a custom user component? I would like to store some additional data from users outside of what is in com_user and vm_user_info. A custom component would also be convenient for applying operations on all the users (via custom functions).

If I cannot share a custom component's tables, what about virtuemart's ability to add custom user fields? Are virtuemart's extra user fields shared between sites?

Thanks very much for your time!

You can add columns in the existing #__users or #__vm_user_info without any problem.
When we sharing the table all the columns are shared.

Becarefull that MySQL does not refresh automatically the column of the shared tables when you modify its structure after the sharing.
If you modify the table where is physically create the "custom" fields, you have to unshare/reshare the extention to refresh the shared table with the new structure.
This is a MySQL constrain that store a snapshot of all the fields shared at the moment that the sharing is decided. So add new columns require to delete/rebuild the MySQL sharing.
This is not a problem as the sharing just consists in creating new views with the additional column.

This is true for any extension and not only for VirtueMart or the users.
This is the case for example of extension like CK_Forms that can be shared and where you have to unshare/reshare when you change the layout of a form.

Thanks very much!